The Safety and Efficacy of MRG003 With or Without Putrelimab in Recurrent or Metastatic Salivary Gland Cancer: a Single-center, Open-label Cohort Study

This study is a four-cohort, open-label, single-center Phase II clinical trial aimed at evaluating the efficacy and safety of MRG003 alone or in combination with pertuzumab in patients with recurrent or metastatic adenoid cystic carcinoma (ACC) and other salivary gland cancers (non- ACC SGCs). This study is an exploratory one without a randomized control. After fully informed and signing the informed consent form, eligible subjects will be enrolled in MRG003 treatment \[Cohort 1 (ACC) and Cohort 2 (non-ACC SGCs) \] in the order of the study sequence. After the completion of enrollment in Cohort 1, subsequent eligible ACC subjects will be included in the MRG003 plus pertuzumab treatment (Cohort 3), and after the completion of enrollment in Cohort 2, subsequent eligible non-ACC SGC subjects will be included in the MRG003 plus pertuzumab treatment (Cohort 4). Patients in Cohort 1 and Cohort 2 will receive intravenous infusion of MRG003 on the first day of each treatment cycle at a dose of 2.3 mg/kg. Patients in Cohort 3 and Cohort 4 will receive intravenous infusion of pertuzumab on the first day of each treatment cycle at a dose of 3 mg/kg (up to a maximum of 200 mg), followed by MRG003 at a dose of 2.0 mg/kg at least 30 minutes after the completion of pertuzumab infusion. All patients will receive single-agent or combination therapy every three weeks until the end of two years of treatment or the occurrence of a treatment discontinuation event as specified in the protocol. After the treatment, safety follow-up and survival follow-up will be conducted for each subject. For subjects who end treatment due to reasons other than disease progression or death and have not started a new anti-tumor study, tumor imaging assessment will continue as originally planned until disease progression, initiation of new anti-tumor treatment, withdrawal of informed consent, loss to follow-up, or death, whichever occurs first. During the clinical study, we will establish PDX models for mechanism validation. In addition, it is recommended to analyze the following markers for subjects: IHC: ER, PR, AR, HER2, EGFR; FISH: HER2. Genetic testing is recommended based on the economic conditions of the subjects, but it is not mandatory. For subjects with HER2 3+ or HER2 2+ and FISH positive, it is recommended to receive anti-HER2 treatment first. For subjects who have undergone testing, we will collect the test results. For subjects who have not undergone testing, we will conduct relevant tests.